State v. Post

Decision Date23 May 2007
Docket NumberNo. 2005AP2778-CR.,2005AP2778-CR.
Citation2007 WI 60,733 N.W.2d 634
PartiesSTATE of Wisconsin, Plaintiff-Respondent-Petitioner, v. Robert E. POST, Defendant-Appellant.
CourtWisconsin Supreme Court

For the plaintiff-respondent-petitioner the cause was argued by James M. Freimuth, assistant attorney general, with whom on the briefs was Peggy A. Lautenschlager, attorney general.

For the defendant-appellant there was a brief filed by T. Christopher Kelly, and Kelly & Habermehl, S.C., Madison, and there was oral argument by T. Christopher Kelly.


The petitioner, State of Wisconsin, seeks review of an unpublished court of appeals decision reversing a judgment convicting Robert Post of operating a motor vehicle with a prohibited alcohol concentration, as a fifth offense.1 The State asserts that the court of appeals erred in concluding that Post's deviations within one lane of travel, with nothing more, failed to provide the police officer with the reasonable suspicion to justify an investigative stop of the vehicle. The State, in essence, asks for a bright-line rule that repeated weaving within a single lane provides the reasonable suspicion necessary to justify a traffic stop.

¶ 2 We determine that weaving within a single traffic lane does not alone give rise to the reasonable suspicion necessary to conduct an investigative stop of a vehicle. However, we also determine that under the totality of the circumstances, the police officer did have reasonable suspicion in this case, and that the stop did not violate Post's constitutional right to be free from unreasonable searches and seizures. Accordingly, we reverse the court of appeals.


¶ 3 In February 2004, Sauk Prairie police sergeant Josh Sherman, who had six years of experience as a police officer, was on routine patrol on Water Street in Sauk City. The northbound side of Water Street is approximately 22-24 feet wide from the yellow center line to the curb. It contains a traffic lane and parking lane. There is no line or marking delineating the traffic lane from the parking lane. The parking lane is bounded by the curb.

¶ 4 Sergeant Sherman testified that at approximately 9:30 p.m., he was traveling southbound on Water Street and observed two cars traveling northbound. The second vehicle, a Chevrolet Cavalier driven by Post, was "canted" such that it was driving at least partially in the unmarked parking lane.

¶ 5 After the two cars passed, Sherman turned around to follow them. He did not lose sight of the cars and caught up to them after six or seven blocks. While following the cars, Sherman observed Post's car traveling in a smooth "S-type" pattern. Sherman described the movement as "a smooth motion toward the right part of the parking lane and back toward the center line." He stated that Post's car moved approximately ten feet from right to left within the northbound lane, coming within 12 inches of the center line and to within six to eight feet of the curb. Post's car repeated the S-pattern several times over two blocks. The movement was neither erratic nor jerky, and the car did not come close to hitting any other vehicles or to hitting the curb at the edge of the parking lane. Sherman testified that the manner of Post's driving was a "clue that he may be intoxicated."

¶ 6 After being followed by Sherman for two blocks, both cars signaled and made a left turn onto a cross street. The first car turned into the oncoming traffic lane. The second car, driven by Post, made a proper turn. Sherman activated his emergency lights and both cars pulled over.

¶ 7 Relying on this court's decision in State v. Waldner, 206 Wis.2d 51, 556 N.W.2d 681 (1996), the circuit court determined that Sherman's testimony of "unusual driving" and "drifting even within one's own lane" provided the reasonable suspicion necessary to justify a traffic stop. The court of appeals reversed, concluding that slight deviations within a single travel lane do not give rise to a reasonable suspicion that a driver is intoxicated.


¶ 8 In this case we examine whether a traffic stop violated Post's constitutional rights because it was not based on reasonable suspicion. The question of whether a traffic stop is reasonable is a question of constitutional fact. State v. Knapp, 2005 WI 127, ¶ 19, 285 Wis.2d 86, 700 N.W.2d 899. A question of constitutional fact is a mixed question of law and fact to which we apply a two-step standard of review. State v. Martwick, 2000 WI 5, ¶ 16, 231 Wis.2d 801, 604 N.W.2d 552. We review the circuit court's findings of historical fact under the clearly erroneous standard, and we review independently the application of those facts to constitutional principles. Id.; State v. Payano-Roman, 2006 WI 47, ¶ 16, 290 Wis.2d 380, 714 N.W.2d 548.


¶ 9 This court has never addressed the question of whether a vehicle's weaving within a single lane, without more, provides the reasonable suspicion necessary to justify an investigatory stop of that vehicle. We begin our analysis of this question by reviewing the principles underlying investigatory stops.

¶ 10 The Fourth Amendment to the United States Constitution provides that "[t]he right of the people to be secure in their persons . . . against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause. . . ."2 In Terry v. Ohio, the U.S. Supreme Court allowed that, although investigative stops are seizures within the meaning of the Fourth Amendment, in some circumstances police officers may conduct such stops even where there is no probable cause to make an arrest. 392 U.S. 1, 22, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968). Such a stop must be based on more than an officer's "inchoate and unparticularized suspicion or `hunch.'" Id. at 27, 88 S.Ct. 1868. Rather, the officer "must be able to point to specific and articulable facts which, taken together with rational inferences from those facts, reasonably warrant" the intrusion of the stop. Id. at 21, 88 S.Ct. 1868.

¶ 11 This court adopted the Terry standard for investigative stops in State v. Chambers, 55 Wis.2d 289, 294, 198 N.W.2d 377 (1972). The Wisconsin legislature codified the standard in Wis. Stat. § 968.24(2005-06).3 In interpreting § 968.24 we apply Terry and cases following Terry. State v. Williamson, 113 Wis.2d 389, 399-400, 335 N.W.2d 814 (1983).

¶ 12 Investigative traffic stops are subject to the constitutional reasonableness requirement. Whren v. United States, 517 U.S. 806, 809-10, 116 S.Ct. 1769, 135 L.Ed.2d 89 (1996); State v. Rutzinski, 2001 WI 22, ¶ 14, 241 Wis.2d 729, 623 N.W.2d 516. The burden of establishing that an investigative stop is reasonable falls on the state. State v. Taylor, 60 Wis.2d 506, 519, 210 N.W.2d 873 (1973).

¶ 13 The determination of reasonableness is a common sense test. The crucial question is whether the facts of the case would warrant a reasonable police officer, in light of his or her training and experience, to suspect that the individual has committed, was committing, or is about to commit a crime. State v. Anderson, 155 Wis.2d 77, 83-84, 454 N.W.2d 763 (1990). This common sense approach balances the interests of the State in detecting, preventing, and investigating crime and the rights of individuals to be free from unreasonable intrusions. Waldner, 206 Wis.2d at 56, 556 N.W.2d 681; Rutzinski, 241 Wis.2d 729, ¶ 15, 623 N.W.2d 516; State v. Guzy, 139 Wis.2d 663, 679, 407 N.W.2d 548 (1987). The reasonableness of a stop is determined based on the totality of the facts and circumstances. State v. Williams, 2001 WI 21, ¶ 22, 241 Wis.2d 631, 623 N.W.2d 106; Guzy, 139 Wis.2d at 679, 407 N.W.2d 548.

¶ 14 The State contends that Sergeant Sherman had reasonable suspicion to stop Post. It advocates the view that repeated weaving of a motor vehicle within a single lane (absent an obvious innocent explanation) provides the reasonable suspicion to make an investigatory stop. While we agree that the facts of the case give rise to a reasonable suspicion that Post was driving while intoxicated and that the investigative stop was reasonable, we reject the bright-line rule that repeated weaving within a single lane alone gives rise to reasonable suspicion. Rather, our determination is based on the totality of the circumstances, in accord with Wisconsin jurisprudence.

¶ 15 In Waldner, this court addressed the issue of investigative stops based on reasonable suspicion that a person is driving while intoxicated. There, a police officer observed the defendant's car traveling at a slow speed. The car stopped at an intersection that had no stop sign or traffic light, turned onto a cross-street, and accelerated "at a high rate of speed" (though not exceeding the speed limit). 206 Wis.2d at 53, 556 N.W.2d 681. The officer then observed the car pull into a legal parking space, where the defendant opened the car door and poured what appeared to be "a mixture of liquid and ice" from a plastic glass onto the roadway. Id. When the officer pulled near the defendant and identified himself, the defendant began to walk away, at which point the officer made an investigative stop of the defendant. Id. at 53-54, 556 N.W.2d 681.

¶ 16 The defendant in Waldner argued that the stop was unreasonable on the ground that it was based upon the officer's inchoate hunch, and not on a reasonable suspicion. This court determined that the search was based on a reasonable suspicion. It noted that the stop was based on a number of specific, articulable facts, including the car's varying speeds and stopping at an intersection without a stoplight or sign, and the driver's pouring out a cup of liquid and ice. The court recognized that each of these facts alone would be insufficient to provide reasonable suspicion. However, it explained that cumulatively they were sufficient to support an inference that the driver was intoxicated:

Any one of these facts, standing alone, might...

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